This invention relates to a method and apparatus for manufacturing plastic tubes for making bags. The tubes have shaped profiles integral with the plastic material on the inner surface thereof with the profiles being shaped so as to form a male rib and a female rib-receiving groove which are occlusive with respect to each other so as to form a reclosable bag from the tubing.
In making the tubular bag material it is molded into a long continuous tube obtained by extruding from an extruding die head under heated state through an extrusion gap in the die head. The die head is shaped to provide the profiles on the inner surface thereof integral with the plastic material of the tube. The tube is distended so that the walls do not touch by air within the tube and cooling means such as air blown surrounding the tube is provided to cool the tube body. The tube is then flattened by means of a pair of rolls.
In accordance with the present invention, the tube is then guided for interengaging the rib and groove profiles preferably in a continuous action as the flattened bag is received from the extruding and cooling apparatus.
The bag material which is now flat and maintaining its occluded state can be finished into individual bags by cutting followed by sealing the cut edges. In actual practice, however, owing to the necessity of accomplishing printing of such as trademarks, trade names, etc. on the bag surface, the bag material that has been formed in a flat and continuous state, as described hereinabove, is first wound up on a reel, transferred to the printing step where after printing it is rewound on the reel and thereafter cut and the cut edges simultaneously sealed.